Lever system for driving mirrors of a lidar transmitter

ABSTRACT

A lever is used to rotate a microelectromechanical systems (MEMS) mirror. The lever can be used to provide more torque from a vertical comb drive. The MEMS mirror can be part of an array of micro mirrors used for beam steering a laser in a Light Detection and Ranging (LiDAR) system for an autonomous vehicle.

CROSS-REFERENCES TO RELATED APPLICATIONS

The following eight U.S. patent applications (which includes the presentapplication) are being filed concurrently, and the entire disclosures ofthe other applications are incorporated by reference into thisapplication for all purposes:

Application Ser. No. 16/213,990, filed Dec. 7, 2018, entitled“MULTI-THRESHOLD LIDAR DETECTION”;

Application Ser. No. 16/213,992, filed Dec. 7, 2018, entitled “MIRRORASSEMBLY FOR LIGHT STEERING”;

Application Ser. No. 16/214,010, filed Dec. 7, 2018, entitled “COUPLEDAND SYNCHRONOUS MIRROR ELEMENTS IN A LIDAR-BASED MICRO-MIRROR ARRAY;

Application Ser. No. 16/214,013, filed Dec. 7, 2018, entitled “COUPLEDAND SYNCHRONOUS MIRROR ELEMENTS IN A LIDAR-BASED MICRO-MIRROR ARRAY;

Application Ser. No. 16/213,995, filed Dec. 7, 2018, entitled“NON-LINEAR SPRINGS TO UNIFY THE DYNAMIC MOTION OF INDIVIDUAL ELEMENTSIN A MICRO-MIRROR ARRAY”;

Application Ser. No. 16/213,997, filed Dec. 7, 2018, entitled“NON-LINEAR SPRINGS TO UNIFY THE DYNAMIC MOTION OF INDIVIDUAL ELEMENTSIN A MICRO-MIRROR ARRAY”;

Application Ser. No. 16/213,999, filed Dec. 7, 2018, entitled “A LEVERSYSTEM FOR DRIVING MIRRORS OF A LIDAR TRANSMITTER”; and

Application Ser. No. 16/214,001, filed Dec. 7, 2018, entitled “SYSTEMAND METHODS FOR CONTROLLING MICRO-MIRROR ARRAY”.

BACKGROUND

Light steering typically involves the projection of light in apre-determined direction to facilitate, for example, the detection andranging of an object, the illumination and scanning of an object, or thelike. Light steering can be used in many different fields ofapplications including, for example, autonomous vehicles, medicaldiagnostic devices, etc.

Modern vehicles are often fitted with a suite of environment detectionsensors that are designed to detect objects and landscape featuresaround the vehicle in real-time that can be used as a foundation formany present and emerging technologies such as lane change assistance,collision avoidance, and autonomous driving capabilities. Some commonlyused sensing systems include optical sensors (e.g., infra-red, cameras,etc.), radio detection and ranging (RADAR) for detecting presence,direction, distance, and speeds of other vehicles or objects,magnetometers (e.g., passive sensing of large ferrous objects, such astrucks, cars, or rail cars), and light detection and ranging (LiDAR).

LiDAR typically uses a pulsed light source and detection system toestimate distances to environmental features (e.g., vehicles,structures, etc.). In some systems, a laser or burst of light (pulse) isemitted and focused through a lens assembly and a reflection of thepulse off of an object is collected by a receiver. A time-of-flight(TOF) of the pulse can be measured from the time of emission to the timethe reflection is received, which may manifest as a single data point.This process can be repeated very rapidly over any desired range(typically 360 degrees over a 2D plane for ground-based vehicles, and a3D region for aircraft) to form a collection of points that aredynamically and continuously updated in real-time, forming a “pointcloud.” The point cloud data can be used to estimate, for example, adistance, dimension, and location of the object relative to the LiDARsystem, often with very high fidelity (e.g., within 5 cm).

Despite the promise that LiDAR and other sensing systems bring to thecontinued development of fully autonomous transportation, there arechallenges that limit its widespread adoption. LiDAR systems are oftenexpensive, large, and bulky. In some cases, multiple emitters may beneeded to accurate track a scene, particularly for systems that requireaccuracy over a large range and field-of-view (FOV). While significantstrides have been made to push autonomous vehicle technology to greatercommercial adoption, more improvements are needed.

BRIEF SUMMARY

In certain embodiments, a device for beam steering in a Light Detectionand Ranging (LiDAR) system of an autonomous vehicle is disclosed. Thedevice can comprise a mirror, a combdrive actuator, a lever, and/or ahinge. The mirror comprises a reflective surface and a supporting beam.The supporting beam is configured to rotate the reflective surface byforce being applied to the supporting beam. The combdrive actuator isconfigured to apply a torque to the supporting beam, wherein thesupporting beam is mechanically between the combdrive actuator and thereflective surface. The lever mechanically couples the combdriveactuator with the supporting beam, wherein the lever is configured toapply a force to the supporting beam. The hinge couples the lever withthe supporting beam, wherein the hinge is configured to allow forarticulated movement between the lever and the supporting beam.

In some embodiments, the combdrive actuator applies a force to themirror such that the mirror rotates in an opposite direction as arotation of the combdrive actuator; the supporting beam is a post on oneside of the mirror; the combdrive actuator is a first combdriveactuator; the torque is a first torque; the device further comprises asecond combdrive actuator on a same side of the mirror as the firstcombdrive actuator, the second combdrive actuator is mechanicallycoupled with the supporting beam, and/or the second combdrive actuatoris configured to apply a second torque to the supporting beam; the hingeis a first hinge; the lever is a first lever; the device furthercomprises: a second lever coupled with the second combdrive actuator,and/or a second hinge that mechanically couples the second lever withthe supporting beam; the second hinge is configured to provide forarticulated movement between the second lever and the supporting beam;the device further comprises an actuator with a spring configured toharmonically oscillate the mirror about a first axis; the supportingbeam is configured to rotate the reflective surface about a second axisand the first axis is not parallel to the second axis; a rotor of thecombdrive actuator rotates about a first axis, the supporting beam isconfigured to rotate the reflective surface about a second axis, thefirst axis is parallel with the second axis, and the hinge is closer tothe second axis than the first axis; the supporting beam is a firstsupporting beam; the device further comprises: a second supporting beamon an opposite side of the mirror than the first supporting beam, asecond combdrive actuator on a same side of the mirror as the firstcombdrive actuator, wherein the second combdrive actuator is coupledwith the first supporting beam, a third combdrive actuator on theopposite side of the mirror, wherein the third combdrive actuator iscoupled with the second supporting beam, and/or a fourth combdriveactuator on the opposite side of the mirror, wherein the fourthcombdrive actuator is coupled with the second supporting beam; thedevice further comprises a first actuator and a second actuatorconfigured to rotate the mirror about a first axis, the first combdriveactuator, the second combdrive actuator, the third combdrive actuator,and the fourth combdrive actuator are configured to rotate the mirrorabout a second axis, and the first axis is not parallel to the secondaxis; the lever and the hinge are made from a silicon crystal layer of asemiconductor wafer; and/or the reflective surface is rectangular.

In certain embodiments, a method of providing torque for beam steeringin a Light Detection and Ranging (LiDAR) system is disclosed. The methodcomprises applying power to a combdrive actuator; rotating a lever usingthe combdrive actuator, wherein the lever is coupled to a rotor of thecombdrive actuator; applying a torque to a supporting beam of a mirrorusing the lever, wherein the mirror comprises a reflective surface;articulating a hinge, wherein the hinge is between the lever and thesupporting beam and provides for articulated movement between the leverand the supporting beam; and/or rotating the reflective surface of themirror based on rotation of the lever.

In some embodiments, the combdrive actuator is a comb drive having aplurality of stator fingers and a plurality of rotor fingers; the mirroris part of a mirror array, and the method further comprises rotating themirror in synchronization with other mirrors of the mirror array tosteer an optical beam reflected by the mirror array; the combdriveactuator is a first combdrive actuator; the lever is a first lever; thetorque is a first torque; the hinge is a first hinge; the method furthercomprises: applying power to a second combdrive actuator, rotating asecond lever using the second combdrive actuator, wherein the secondlever is coupled to a rotor of the second combdrive actuator, applying asecond torque to the supporting beam using the second lever,articulating a second hinge, wherein the second hinge is between thesecond lever and the supporting beam and provides for articulatedmovement between the second lever and the supporting beam, and/orrotating the reflective surface of the mirror based on rotation of thesecond lever.

In certain embodiments, a device for beam steering in a Light Detectionand Ranging (LiDAR) system of an autonomous vehicle comprises a mirror,a first combdrive actuator, a lever, and/or a second combdrive actuator.The mirror comprises a reflective surface and/or a supporting beam,wherein the supporting beam is configured to rotate the reflectivesurface by force being applied to the supporting beam. The firstcombdrive actuator is coupled with the supporting beam and is configuredto apply a torque to the supporting beam. The supporting beam ismechanically between the first combdrive actuator and the reflectivesurface. The lever is between the second combdrive actuator and thesupporting beam. The second combdrive actuator is configured to use thelever to apply a force to the supporting beam. The supporting beam ismechanically between the second combdrive actuator and the mirror.

In some embodiments, the supporting beam is mechanically between thefirst combdrive actuator and the second combdrive actuator; the firstcombdrive actuator is mechanically between the supporting beam and thesecond combdrive actuator; a hinge is mechanically between the firstcombdrive actuator and the second combdrive actuator; the secondcombdrive actuator is driven 180 degrees out of phase with the firstcombdrive actuator; and/or the first combdrive actuator rotates in anopposite direction as a rotation of the mirror.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for purposes ofillustration only and are not intended to necessarily limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

The detailed description is set forth with reference to the accompanyingfigures.

FIG. 1 shows an autonomous driving vehicle utilizing aspects of certainembodiments of disclosed techniques.

FIG. 2 illustrates an example of a light steering transmitter, accordingto certain embodiments.

FIG. 3 depicts part of an embodiment of a mirror assembly.

FIG. 4 depicts an embodiment of a lever used for rotating a reflectivesurface.

FIG. 5 depicts a simplified side view of the embodiment of the lever forrotating the reflective surface.

FIG. 6 depicts a simplified perspective view of an embodiment combdriveactuators for rotation a mirror.

FIG. 7 illustrates a flowchart of an embodiment of a method of using alever to provide torque for rotating a reflective surface.

FIG. 8 illustrates another embodiment of using levers for rotating areflective surface.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

Aspects of the present disclosure relate generally to mirrors used forbeam steering, and without limitation, to beam steering in a LightDetection and Ranging (LiDAR) system (e.g., for use in a system with anautonomous vehicle). Other examples of beam steering include: the headlight of a manually-driven vehicle can include the light steeringtransmitter, which can be controlled to focus light towards a particulardirection to improve visibility for the driver; and optical diagnosticequipment, such as an endoscope, can include a light steeringtransmitter to steer light in different directions onto an object in asequential scanning process to obtain an image of the object fordiagnosis.

A light steering transmitter may include a movable mirror assembly tofacilitate configurable and precise control of a light projection. Amirror can be moved (e.g., rotated) by actuators to reflect (and steer)light from a light source towards a pre-determined angle. Light steeringcan be implemented by way of a mirror assembly included in the lightsteering transmitter. A mirror in the mirror assembly can be moved byactuators to steer light from a light source towards a pre-configureddirection. For improved integration, the mirror assembly, actuators, andthe control circuitries that configure the actuators to set the anglesof projection can be integrated on a semiconductor substrate, with themirror assembly and actuators can be formed as microelectromechanicalsystems (MEMS) on the semiconductor substrate.

In some examples, a mirror assembly may include a single mirror. Thesingle mirror can be coupled with two pairs of actuators and rotatableon two non-parallel axes (e.g., orthogonal axes). A first pair, or set,of actuators can rotate the mirror around a first axis to steer thelight along a first dimension, whereas a second pair, or set, ofactuators can rotate the mirror around a second axis to steer the lightalong a second dimension. Different combinations of angle of rotationsaround the first axis and the second axis can provide a two-dimensionalFOV.

Actuators moving the mirror about the first axis comprise a spring. Thespring is used so the mirror can be driven to oscillate at a harmonicfrequency, wherein the harmonic frequency is based on a combination of aspring constant of the spring and a mass of the mirror. The actuatorsmoving the mirror about the second axis do not comprise a spring.Instead actuators moving the mirror about the second axis use a DC biasto control steering along the second dimension. Driving the mirror aboutthe first axis at a harmonic frequency requires less force by actuatorsthan driving the mirror about the second axis by actuators using a DCbias. One way to increase the force exerted by actuators driven by DCbias is to make the actuators much longer (e.g., 3, 4, or 5 timeslonger) than actuators driven at a harmonic frequency. However, usinglonger actuators takes up chip space and does not allow for as muchmirror space on the chip for a mirror array. Long device actuators canalso reduce device reliability.

Another way to increase force exerted by actuators, is to have actuatorswith longer rotor and stator fingers and/or have two or more actuatorson one side of a mirror to rotate the mirror about the second axis. Forexample, a lever can be used to link an actuator with the mirror. Byusing a lever, a greater force can be applied to a supporting beam of amirror for more effective rotation of the mirror. In some embodiments,an array of microelectromechanical system (MEMS) mirrors is used inLiDAR scanning system to increase scanning speed and to increasereflective surface area (e.g., one laser beam is reflected by aplurality of MEMS mirrors synchronized to act as one large reflectivearea). By using levers, actuators can be arranged on a chip to make moreroom for reflective surfaces to steer light.

In the following description, various examples of a mirror assembly anda light steering transmitter system will be described. For purposes ofexplanation, specific configurations and details are set forth in orderto provide a thorough understanding of the embodiments. However, it willbe apparent to one skilled in the art that certain embodiments may bepracticed or implemented without every detail disclosed. Furthermore,well-known features may be omitted or simplified in order to prevent anyobfuscation of the novel features described herein.

FIG. 1 illustrates an embodiment of an autonomous vehicle 100 in whichthe disclosed techniques can be implemented. The autonomous vehicle 100includes a LiDAR module 102. LiDAR module 102 allows the autonomousvehicle 100 to perform object detection and ranging in a surroundingenvironment. Based on results of object detection and ranging, theautonomous vehicle 100 can maneuver to avoid a collision with objects.The LiDAR module 102 can include a transmitter 104 and a receiver 106for light steering. The transmitter 104 can project one or more lightpulses 108 at various directions at different times in a scanningpattern, while receiver 106 can monitor for a light pulse 110 which isgenerated by the reflection of light pulse 108 by an object. LiDARmodule 102 can detect the object based on the reception of light pulse110, and can perform a ranging determination (e.g., a distance of theobject) based on a time difference between light pulses 108 and 110and/or based on phase difference between light pulses 108 and 110. Forexample, as shown in FIG. 1, the LiDAR module 102 can transmit lightpulse 108 at a direction directly in front of autonomous vehicle 100 attime T1 and receive light pulse 110 reflected by an object 112 (e.g.,another vehicle) at time T2. Based on the reception of light pulse 110,LiDAR module 102 can determine that object 112 is directly in front ofautonomous vehicle 100. Moreover, based on the time difference betweenT1 and T2, LiDAR module 102 can also determine a distance 114 betweenautonomous vehicle 100 and object 112. The autonomous vehicle 100 canadjust its speed (e.g., slowing or stopping) to avoid collision withobject 112 based on the detection and ranging of object 112 by LiDARmodule 102.

FIG. 2 illustrates an example of internal components of a LiDAR module102. LiDAR module 102 includes the transmitter 104, the receiver 106,and a controller 206, which controls the operations of the transmitter104 and the receiver 106. Transmitter 104 includes a light source 208, alens 210, and a mirror assembly 212. The light source 208 is configuredto generate light pulses 108. In some embodiments, the light source 208is a laser diode. The lens 210 is a collimator lens configured tocollimate light emitted from the light source 208. The receiver 106comprises a lens 214 and a detector 216 (e.g., a photodetector). Thelens 214 is configured to focus light from light pulses 110 onto thedetector 216.

The controller 206 can control the light source 208 to transmit lightpulse 108, which is part of an optical beam 218. The optical beam 218can diverge upon leaving the light source 208. The optical beam 218 iscollimated by passing through lens 210. Lens 210 has an aperture width(e.g., diameter of lens 210), which can set a beam width 220 ofcollimated light incident on the mirror assembly 212.

The optical beam 218 is reflected by the mirror assembly 212 and steeredby the mirror assembly 212 along a projection path 219 towards theobject 112. The mirror assembly 212 includes one or more mirrors 221,which is rotatable. FIG. 2 illustrates the mirror assembly 212 havingone mirror 221, but as to be described below, in some embodiments themirror assembly 212 includes a plurality of mirrors. To reduce loss oflight, the mirror 221 can have a length (and/or width) that matches thebeam width 220. Such an arrangement can enable the mirror assembly 212to reflect and project a larger portion of light and to mitigatedispersion.

The mirror assembly 212 further includes one or more actuators to rotatethe mirror 221. The actuators can rotate mirror 221 about a first axis222, and about a second axis 226. Rotation about the first axis 222 canchange a first angle of the projection path 219 and rotation about thesecond axis 226 can change a second angle of the projection path 219.The controller 206 can control the actuators to produce differentcombinations of angles of rotation around the first axis 222 and thesecond axis 226 such that the movement of the projection path 219 canfollow a scanning pattern 232. The scanning pattern has a first range234 (e.g., horizontal) and a second range 238 (e.g., vertical). Thefirst range 234 and the second range 238 define a field of view (FOV) ofthe transmitter 104. Light from the optical beam 218 reflects from anobject within the FOV, such as object 112, to form light pulse 110,which is a reflected pulse. The light pulse 110 is detected by thereceiver 106.

FIG. 3 is a part of an embodiment of a mirror assembly 212. The mirrorassembly 212 comprises a mirror 221 and an actuator 304. The mirrorcomprises a mirror substrate 308 and a reflective surface 312. Themirror substrate 308 is a substrate for the reflective surface 312 to beapplied to, e.g., sputtering alternating dialectic layers of materialson the substrate to form a Bragg mirror on the substrate as thereflective surface 312.

The actuator 304 comprises a shaft 320, a spring 324, a post 328, and acomb drive. The comb drive comprises a stator 332 and a rotor 336. Insome embodiments, the comb drive is a vertical comb drive having aplurality of stator fingers and plurality of rotor fingers. The spring324 is mechanically coupled with the mirror 221. For example, the spring324 is coupled to the rotor 336; the rotor 336 is coupled to the shaft320, and the shaft 320 is coupled to the mirror substrate 308 of themirror 221. The rotor 336 rotates back and forth around the first axis222, e.g., +/−10, 15, 20, 25, or 30 degrees. As the rotor 336 moves, thespring 324 is twisted and the mirror 221 is rotated. The actuator 304can be configured to work in pairs to move the mirror 221 about thefirst axis 222. In the embodiment shown, a first actuator 304-1 and asecond actuator 304-2 work together as a pair to move the mirror 221about the first axis 222.

The spring 324 is coupled to the rotor 336 and the post 328. The post328 does not rotate. An electrical signal is applied to the comb driveto cause magnetic repulsion and/or attraction between the stator 332 andthe rotor 336. As the rotor 336 rotates, the spring 324 is twisted,storing mechanical energy and applying a torque to the rotor 336 and/orto the shaft 320. As the rotor 336 rotates, the mirror 221 rotatesbecause the mirror 221 is coupled to the rotor 336 by the shaft 320. Anangle of the reflective surface 312 with respect to the light source 208changes as the mirror 221 rotates. The spring 324 and the comb drivemove the mirror 221 to oscillate at a given frequency, thus steering theprojection path 219 of the optical beam 218 back and forth (e.g.,horizontally) within the first range 234. A different actuator and/orcomb drive system moves the mirror 221 about the second axis 226.

In some embodiments, the substrate is part of a silicon-on-insulator(SOI) wafer, and the reflective surface 312 is applied on top of adevice layer of the SOI wafer. The reflective surface 312 is rectangularto provide more reflective surface area of an array of mirrors and/or tomore efficiently use space on a chip. The mirror substrate 308, theshaft 320, the spring 324, the post 328, the stator 332, and/or therotor 336 can be made using photolithography, e.g., the mirror substrate308, the shaft 320, the spring 324, the post 328, the stator 332, and/orthe rotor 336 are etched concurrently from a device layer of an SOIwafer. In some embodiments, electrical elements for the comb drive areformed in the device layer of the SOI wafer.

FIG. 4 depicts an embodiment of a lever used for rotating a reflectivesurface. The lever can be part of a mirror assembly 212. FIG. 4 shows afirst actuator 304-1, a second actuator 304-2, a first combdriveactuator 404-1, and a second combdrive actuator 404-2. The actuators 304and combdrive actuators 404 are used to rotate the reflective surface312 of the mirror 221 about the first axis 222 and the second axis 226.

The first actuator 304-1 and a second actuator 304-2 are used to rotatethe reflective surface 312 about the first axis 222. Rotors 336 of thefirst actuator 304-1 and the second actuator 304-2 rotate about thefirst axis 222 is a similar direction as the reflective surface 312.

The first combdrive actuator 404-1 and the second combdrive actuator404-2 (in combination with a third combdrive actuator and a fourthcombdrive actuator, not shown) are used to rotate the reflective surface312 about the second axis 226. A first supporting beam 408-1 and asecond supporting beam 408-2 extend from the mirror substrate 308 of themirror 221. The first supporting beam 408-1 is mechanically between thefirst combdrive actuator 404-1 and the reflective surface 312 andmechanically between the second combdrive actuator 404-2 and thereflective surface 312. In some embodiments, the supporting beams 408are part of the mirror substrate 308. Accordingly, the mirror 221comprises the reflective surface 312 and the supporting beam 408. Thefirst supporting beam 408-1 extends from one side of the mirrorsubstrate 308. The second supporting beam 408-2 extends from anotherside of the mirror substrate 308. The supporting beam 408 can be anelongated post extending from one side of the mirror substrate 308 ofthe mirror 221. The supporting beam 408 is configured to rotate thereflective surface 312 by a force being applied to the supporting beam408.

The first combdrive actuator 404-1 comprises a first stator 332-1 and afirst rotor 336-1. The first rotor 336-1 rotates about a third axis 412.The third axis 412 is parallel with the second axis 226. The firstcombdrive actuator 404-1 is coupled with the first supporting beam 408-1and is configured to apply a first torque to the first supporting beam408-1 by applying a first force to the first supporting beam 408-1. Afirst lever 420-1 is between the first combdrive actuator 404-1 and thefirst supporting beam 408-1. The first lever 420-1 mechanically couplesthe first rotor 336-1 of the first combdrive actuator 404-1 with thefirst supporting beam 408-1. The first lever 420-1 is used to apply aforce, the first force, to the first supporting beam 408-1. A firsthinge 424-1 mechanically couples the first lever 420-1 with the firstsupporting beam 408-1. The first hinge 424-1 provides for articulated(e.g., flexible) movement between the first lever 420-1 and the firstsupporting beam 408-1. For example, the hinge 424 is configured toexpand and contract as the lever 420 is moved. In some embodiments, afirst stub 425-1 couples the first lever 420-1 to the first hinge 424-1.The first stub 425-1 can be rigidly attached to the first supportingbeam 408-1. The first hinge 424-1 provides for articulated movementbetween the first lever 420-1 and the first supporting beam 408-1 byallowing for articulated movement between the first stub 425-1 and thefirst lever 420-1. In some embodiments, the hinge 424 can be used tolimit rotation of the mirror 221 for non-linear driving of mirrors, asdescribed in U.S. patent application Ser. No. 16/213,995. In someembodiments, the hinge 424 can act as a spring, though normally thehinge 424 does not because the hinge 424 is too soft in a horizontalconstraint (e.g., in the x direction in FIG. 4) to be considered aspring.

The second combdrive actuator 404-2 comprises a second stator 332-2 anda second rotor 336-2. The second rotor 336-2 rotates about a fourth axis426. The fourth axis 426 is parallel with the second axis 226. Thesecond combdrive actuator 404-2 is coupled with the first supportingbeam 408-1 and is configured to apply a second torque to the firstsupporting beam 408-1 by applying a second force to the first supportingbeam 408-1. A second lever 420-2 is between the second combdriveactuator 404-2 and the first supporting beam 408-1. The second lever420-2 mechanically couples the second rotor 336-2 of the secondcombdrive actuator 404-2 with the first supporting beam 408-1. Thesecond lever 420-2 is used to apply a force, the second force, to thefirst supporting beam 408-1. A second hinge 424-2 mechanically couplesthe second lever 420-2 with the first supporting beam 408-1. The secondhinge 424-2 provides for articulated movement between the second lever420-2 and the first supporting beam 408-1. In some embodiments, a secondstub 425-2 couples the second lever 420-2 to the second hinge 424-2. Thesecond stub 425-2 can be rigidly attached to the first supporting beam408-1. The second hinge 424-2 provides for articulated movement betweenthe second lever 420-2 and the first supporting beam 408-1 by allowingfor articulated movement between the second stub 425-2 and the secondlever 420-2. The first supporting beam 408-1 is mechanically between thefirst combdrive actuator 404-1 and the second combdrive actuator 404-2.

A third hinge 424-3 couples a third combdrive actuator with the secondsupporting beam 408-2, and a fourth hinge 424-4 couples a fourthcombdrive actuator with the second supporting beam 408-2, similar to thefirst combdrive actuator 404-1 and the second combdrive actuator 404-2being coupled with the first supporting beam 408-1. For example, thethird combdrive actuator applies a third torque to the second supportingbeam 408-2 and the fourth combdrive actuator applies a fourth torque tothe second supporting beam 408-2, wherein the first torque, the secondtorque, the third torque, and the fourth torque are configured to rotatethe mirror 221 in the same direction. Put another way, the first torque,the second torque, the third torque, and the fourth torque can bedefined by vectors, and the vectors point in the same direction, so thatthe first torque, the second torque, the third torque, and the fourthtorque constructively add. The third combdrive actuator and the fourthcombdrive actuator are on opposite sides of the mirror 221 than thefirst combdrive actuator 404-1 and the second combdrive actuator 404-2.Similarly, torques created by the first actuator 304-1 and the secondactuator 304-2 point in the same direction and constructively add.

In some embodiments, a spring 324 is coupled with the first rotor 336-1,and/or a spring is coupled with the second rotor 336-2, similarly asdescribed in conjunction with the first actuator 304-1. However, in theembodiment shown in FIG. 4, there are not springs 324 coupled with thefirst rotor 336-1 or the second rotor 336-2. The combdrive actuators 404provide a DC bias to rotate the mirror 221 about the second axis 226.For example, as actuators 304 are rotating the mirror 221 at a resonantfrequency about the first axis 222 (to scan the first range 234 of thescanning pattern 232), the combdrive actuators 404 are stepping rotationof the mirror 221 about the second axis 226 (to scan the second range238 of the scanning pattern 232). Since driving an actuator 304 at aharmonic frequency of the spring 324 takes less force, the actuators 304can be smaller than the combdrive actuators 404, which provide a DCbias. The first hinge 424-1 is closer to the second axis 226 than thethird axis 412 so that the first rotor 336-1 does not have to rotate asmuch to cause a greater rotation of the first supporting beam 408-1and/or to apply a greater force to the first supporting beam 408-1.

FIG. 5 depicts a simplified side view of the embodiment of the lever forrotating the reflective surface 312. The first lever 420-1 rotates aboutthe third axis 412 and is coupled with the first supporting beam 408-1via the first hinge 424-1 and the first stub 425-1. As the first lever420-1 rotates clockwise about the third axis 412, the first lever 420-1exerts a first force on the first supporting beam 408-1 to cause thefirst supporting beam 408-1 to rotate counter clockwise. As the firstsupporting beam 408-1 rotates counter clockwise, the reflective surface312 is rotated counter clockwise about the second axis 226. Accordingly,the first combdrive actuator 404-1 rotates in an opposite direction of arotation of the mirror 221. The first hinge 424-1 provides flexibility(e.g., the first hinge 424-1 expands and contracts in the x direction)between the first lever 420-1 and the first supporting beam 408-1 (e.g.,between the first lever 420-1 and the first stub 425-1, which is rigidlyattached to the first supporting beam 408-1).

The second lever 420-2 rotates about the fourth axis 426 and is coupledwith the first supporting beam 408-1 via the second hinge 424-2 and thesecond stub 425-2. As the second lever 420-2 rotates clockwise about thefourth axis 426, the second lever 420-2 exerts a second force on thefirst supporting beam 408-1 to cause the first supporting beam 408-1 torotate counter clockwise. As the first supporting beam 408-1 rotatescounter clockwise, the reflective surface 312 is rotated counterclockwise about the second axis 226. Accordingly, the second combdriveactuator 404-2 rotates in an opposite direction of a rotation of themirror 221. The second hinge 424-2 provides flexibility (e.g., thesecond hinge 424-2 expands and contracts in the x direction) between thesecond lever 420-2 and the first supporting beam 408-1 (e.g., betweenthe second lever 420-2 and the second stub 425-2, which is rigidlyattached to the first supporting beam 408-1).

By using levers 420, a greater force can be applied to the supportingbeam 408 for more effective rotation of the supporting beam 408.Applying a greater force to rotate the supporting beam 408 can bebeneficial, in some embodiments, because the mirror 221 can be harder torotate about the second axis 226 compared to the first axis 222 sincethe mirror 221 is not being driven at a harmonic frequency for rotationabout the second axis 226. By using a DC bias to electrically controlscanning (e.g., scanning speed) in the second range 238, the complexityof tuning two different harmonic oscillators (e.g., one harmonicoscillator for rotating the mirror 221 about the first axis 222 and asecond harmonic oscillator for rotating the mirror 221 about the secondaxis 226) with each other is removed. The angle of rotation of thecombdrive actuator 404 can also be different than the angle of rotationof the supporting beam 408 because of different lengths of the lever420. For example, the supporting beam 408 can be configured to rotate upto plus and minus 30 degrees. The combdrive actuator 404 and lever 420can be configured to rotate plus and minus 15 degrees to rotate thesupporting beam 408 plus and minus 30 degrees.

FIG. 6 depicts a perspective view of an embodiment of comb driveactuators for rotating a mirror. FIG. 6 shows the first actuator 304-1and the second actuator 304-2 used to rotate the reflective surface 312about the first axis 222. The first rotor 336-1 of the first combdriveactuator 404-1, the second rotor 336-2 of the second combdrive actuator404-2, a third rotor 336-3 of the third combdrive actuator, and a fourthrotor 336-4 of the fourth combdrive actuator are shown. The first lever420-1 connects the first rotor 336-1 with the first supporting beam408-1. The second lever 420-2 connects the second rotor 336-2 with thefirst supporting beam 408-1. The third lever 420-3 connects the thirdrotor 336-3 with the second supporting beam 408-2. The fourth lever420-4 connects the fourth rotor 336-4 with the second supporting beam408-2. The rotors 336 and levers 420 are used to rotate the reflectivesurface 312 about the second axis 226.

FIG. 7 illustrates a flowchart of an embodiment of a method 700 ofproviding torque for bean steering in a light detection and ranging(LiDAR) system. Method 700 begins in step 704 with applying power to acombdrive actuator (e.g., the first combdrive actuator 404-1). The firstcombdrive actuator 404-1 is used to rotate a lever (e.g., the firstlever 420-1), step 708, to apply a torque (a first torque) to asupporting beam (e.g., the first supporting beam 408-1) of a mirror(e.g., mirror 221), step 712. The first combdrive actuator 404-1 movesthe first rotor 336-1, which moves the first lever 420-1, which appliesa force (and torque) to the first supporting beam 408-1. The forcecauses the first supporting beam 408-1 to rotate.

As the force/torque is applied, the supporting beam rotates. As thesupporting beam rotates, a hinge (e.g., the first hinge 424-1) is ajoint made to flex to allow for articulated movement between the leverand the supporting beam, step 716. As the supporting beam rotates, areflective surface (e.g., the reflective surface 312) of the mirror alsorotates (e.g., about the second axis 226), step 720. A second, third,and/or fourth force/torque can be applied to one or more supportingbeams using a second combdrive actuator and/or second hinge, a thirdcombdrive actuator and/or third hinge, and/or a fourth combdriveactuator and/or a fourth hinge.

In some embodiments, the mirror is part of a mirror array, and themethod further comprises moving the mirror in sync with other mirrors inthe mirror array to steer an optical beam reflected by a plurality ofmirrors in the mirror array.

FIG. 8 illustrates another embodiment of using levers for rotating areflective surface. FIG. 8 illustrates some variations that could beused for moving the reflective surface 312 (e.g., in combination withfeatures from other embodiments). FIG. 8 depicts a first combdriveactuator 404-1, a second combdrive actuator 404-2, and a third combdriveactuator 404-3 on one side of the mirror 221. The third combdriveactuator 404-3 rotates about an axis that is coincident with the secondaxis 226. The first lever 420-1 and the first hinge 424-1 aremechanically coupled with the first supporting beam 408-1 through thethird combdrive actuator 404-3 (i.e., the first lever 420-1 and thefirst hinge 424-1 are between the first combdrive actuator 404-1 and thethird combdrive actuator 404-3; the third combdrive actuator 404-3 ismechanically between the first combdrive actuator 404-1 and the firstsupporting beam 408-1). The third combdrive actuator 404-3 rotates inthe same direction as the mirror and 180 degrees out of phase with thefirst combdrive actuator 404-1. The second combdrive actuator 404-2 iscoupled with the mirror 221 by the second hinge 424-2 being coupled to aside of the mirror 221, where the side of the mirror 221 is considered asupporting beam.

The ensuing description provides preferred exemplary embodiment(s) only,and is not intended to limit the scope, applicability, or configurationof the disclosure. Rather, the ensuing description of the preferredexemplary embodiment(s) will provide those skilled in the art with anenabling description for implementing a preferred exemplary embodiment.It is understood that various changes may be made in the function andarrangement of elements without departing from the spirit and scope asset forth in the appended claims.

The specific details of particular embodiments may be combined in anysuitable manner without departing from the spirit and scope ofembodiments of the invention. However, other embodiments of theinvention may be directed to specific embodiments relating to eachindividual aspect, or specific combinations of these individual aspects.

Also, it is noted that the embodiments may be described as a processwhich is depicted as a flowchart, a flow diagram, a data flow diagram, astructure diagram, or a block diagram. Although a flowchart may describethe operations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be re-arranged. A process is terminated when itsoperations are completed, but could have additional steps not includedin the figure. A process may correspond to a method, a function, aprocedure, a subroutine, a subprogram, etc.

A recitation of “a”, “an”, or “the” is intended to mean “one or more”unless specifically indicated to the contrary.

All patents, patent applications, publications, and descriptionsmentioned here are incorporated by reference in their entirety for allpurposes. None is admitted to be prior art.

What is claimed is:
 1. A device for beam steering in a Light Detectionand Ranging (LiDAR) system of an autonomous vehicle, the devicecomprising: a mirror comprising: a reflective surface; and a supportingbeam, wherein the supporting beam is configured to rotate the reflectivesurface by force being applied to the supporting beam; a combdriveactuator, wherein: the combdrive actuator is configured to apply atorque to the supporting beam; and the supporting beam is mechanicallybetween the combdrive actuator and the reflective surface; a levermechanically coupling the combdrive actuator with the supporting beam,wherein the lever is configured to apply a force to the supporting beam;a hinge coupling the lever with the supporting beam, wherein the hingeis configured to allow for articulated movement between the lever andthe supporting beam; and an actuator with a spring configured toharmonically oscillate the mirror about a first axis, wherein thesupporting beam is configured to rotate the reflective surface about asecond axis, and wherein the first axis is not parallel to the secondaxis.
 2. The device of claim 1, wherein the combdrive actuator applies aforce to the mirror such that the mirror rotates in an oppositedirection as a rotation of the combdrive actuator.
 3. The device ofclaim 1, wherein the supporting beam is a post on one side of themirror.
 4. The device of claim 3, wherein: the combdrive actuator is afirst combdrive actuator; the torque is a first torque; the devicefurther comprises a second combdrive actuator on a same side of themirror as the first combdrive actuator; the second combdrive actuator ismechanically coupled with the supporting beam; and the second combdriveactuator is configured to apply a second torque to the supporting beam.5. The device of claim 4, wherein: the hinge is a first hinge; the leveris a first lever; the device further comprises: a second lever coupledwith the second combdrive actuator; and a second hinge that mechanicallycouples the second lever with the supporting beam; and the second hingeis configured to provide for articulated movement between the secondlever and the supporting beam.
 6. The device of claim 1, wherein: arotor of the combdrive actuator rotates about a third axis; thesupporting beam is configured to rotate the reflective surface about afourth axis; the first axis is parallel with the second axis; and thehinge is closer to the second axis than the first axis.
 7. The device ofclaim 1, wherein: the combdrive actuator is a first combdrive actuator;the supporting beam is a first supporting beam; and the device furthercomprises: a second supporting beam on an opposite side of the mirrorthan the first supporting beam; a second combdrive actuator on a sameside of the mirror as the first combdrive actuator, wherein the secondcombdrive actuator is coupled with the first supporting beam; a thirdcombdrive actuator on the opposite side of the mirror, wherein the thirdcombdrive actuator is coupled with the second supporting beam; and afourth combdrive actuator on the opposite side of the mirror, whereinthe fourth combdrive actuator is coupled with the second supportingbeam.
 8. The device of claim 7, wherein: the actuator is a firstactuator, and the device further comprises a second actuator configuredto rotate the mirror about the first axis; the first combdrive actuator,the second combdrive actuator, the third combdrive actuator, and thefourth combdrive actuator are configured to rotate the mirror about thesecond axis.
 9. The device of claim 1, wherein the lever and the hingeare made from a silicon crystal layer of a semiconductor wafer.
 10. Thedevice of claim 1, wherein reflective surface is rectangular.